High performance, fiber-reinforced, organic matrix composites provide lightweight but strong structures. In such materials, the organic matrix is generally a thermosetting material. The most common thermosetting matrices used are the epoxies. The inherently flammable nature of many of the epoxies used, however, limits their widespread application for fire-resistant composites.
Cyclomatrix polyorganophosphazenes, which consist of a network of phosphazene rings coupled by multifunctional organic residues at the phosphorus atoms, provide heat- and fire-resistant polymer systems. Some aspects of the synthesis of organophosphazene-based multifunctional epoxies and their curing to polymers have been reported in the literature, such as in W. Bloom, U.S. Pat. No. 3,412,045 (1968); Chem. Abstr., 70, 29723 (1969); H. Tsuchida, Kokai Tokkyo Koho 73,38687 (1973); Chem. Abstr. 81, 64307k (1974); Ya P. Belyayev and M. S. Trizno, Plast. Massy, 5, 77 (1974); Chem. Abstr., 81 153388c (1974); Ya P. Belkyayev and M. S. Trizno, Plast. Massy. 8, 7 (1975); Chem. Abstr., 83, 11241 (1975); H. Kawamura, Kokai Tokkyo Koho 73,37499 (1973); Chem. Abstr. 80, 15635 (1974); H. Kawamura, Kokai Tokkyo Koho 73,25758 (1973); Chem. Abstr., 80, 109260 and 109261 (1974); M. Wajima, R. Tadas, and T. Nakamura, Kokai Tokkyo Koho, 73,76998 (1973); Chem. Abstr. 80, 109318 (1974); H. Maki, Kokai Tokkyo Koho 76,21000 (1976); Chem. Abstr., 84, 165720 (1976); L. A. Alexeenko, V. V. Kireev, and D. F. Kupetov, Plast. Massy, 11, 13-14 (1978); Chem. Abstr., 90, 104709 (1979); L. A. Alexeenko, U.S.S.R. Pat. 737412 (1980); Chem. Abstr., 93, 133324 (1980); K. L. Paciorek, NASA-CR-165147-SN-8342-F; Chem. Abstr., 94, 122476 (1981); and E. Devadoss, J. Appl. Polym. Sci., 28, 921-941 (1983).
Other references of interest include Macromolecules, 16, 1250, (1983) and J. Polymer Sci., Chem. Ed., 22, 927 (1984), as well as U.S. Pat. Nos. 4,316,006; 4,107,146; 4,124,557 and 4,405,738.
The polyorganophosphazene-epoxy systems obtained in most of these cases are based on products formed by mixing multifunctional reactants in which the amino or epoxy groups required for the reaction are not directly attached to the cyclotriphosphazene moiety. The resulting products are complex and usually thermally unstable.